How do Control Line Speed models go so fast?

Just as there are certain components that help a model airplane to fly, there are certain other designs that help it to fly fast. Everything on the outside of a Control Line model is designed to reduce drag: smaller size, smaller tails, no vertical stabilizer, engine casing, smooth fuselage, etc. However, there are other ways to optimize speed on the model internally.

Experimentation with what powers the model has resulted in many innovations over the years, and each has their benefits.

Fuel Cocktail
Modelers have experimented with different mixtures of fuel to see what would go fastest. All kinds of fuels have been tested: Castor oil, nitro, and alcohol. Different percentages of these fuels were/are combined and tested to find the best cocktail that gets the model to fly fastest. For example, 37.5% Nitro 37.5% Alcohol 25% Castor Oil made James D. Walter’s Class C models fly over 130 mph in 1952. Diesel has rarely been associated with speed; however, it has been seen in competition.

Engines
Engines for model airplanes come in a variety of shapes and sizes, but what matters for speed is the power. Glow, spark, ignition, Co2, diesel, or pulse jet. Regardless which engine type and make a model uses, its class is determined on its power per cubic inch:
Class ½ A: .0000- .0504
Class ½ A Proto: .0000- .0504
Class A: .0505- .1525
Class B: .1526- .3051
Class C: .2900-.4000
Class D: .4001- .6500
Class Sport Speed 21: .198- .2135
.21 Proto: .00- .2135
Formula 40: .2800- .4028
Jet

Electricity
Electric-powered models have been around since the early 20th century. Possibly the first electric powered model was produced by A.E. Rittenhouse Company of Honeoye Falls, New York in 1913. These models were attached to the ceiling and would fly in a circle. Their flight was sustained with a combination of centrifugal force and gravity. They could attain an actual speed of 12 mph on 8 dry cells.

After that, electric power was experimented with in Radio Control models during the 1950s and 1960s, but it did not become a commercially viable option until the 1970s. In the 70’s, Mr. Bob Boucher, then President of co-founder of Astro Flight, pushed for electric-powered models because of their benefits. However, the first electric powered Control Line model was not mass distributed until 2007, with the “Flying Clown”.

Sources:
Boucher, Robert J. The Quiet Revolution: The Complete Manual of Electric Propulsion Systems.  Astro Flight, 1979.
AMA, Control Line Speed Competition Regulations Rules Governing Model Aviation Competition in the United States, 2016.
Strollo, John.  “C/L Speed Review” Anglefire.com. Blog post. no date.

Thanks to intern Kayla Al Ameri for writing this blog post, and her work on this exhibit!

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